The alleged Arizona shooter who killed six people and wounded another 12 including US Representative Gabrielle Giffords has been identified as 22 year old Jared Lee Loughner.

The shooting took place as Congresswoman Giffords held a constituent meeting at a Safeway grocery store in Tucson on Saturday.

What's believed to be a posting on You Tube by Loughner begins with the words "My final thoughts: Jared Lee Loughner." The posting contains confused rantings.

The posting suggests he did not expect to survive the shooting, and says he "defines terrorism."

"If I define terrorist then a terrorist is a person who employs terror or terrorism, especially as a political weapon. I define terrorism," he wrote on the video.

He said he was a United States military recruit at MEPS in Phoenix, with references to receiving one mini bible before the recruit tests.

"I didn't write a belief on my army application, and the recruiter wrote on the application: none," he wrote.

He said the government was "implying mind control and brainwash on the people by controlling grammar."

Rep. Giffords is reported to have survived the attack after being shot in the head and had undergone surgery at a local hospital.

Arizona state senator Linda Lopez told Fox, "We just heard that she is responding to commands. She made it through surgery."

The chief of the Pima County police department, Rich Castigar, said that 18 people had been shot in the incident and that six people are dead.

He said a 22 year old man is in custody, who has had limited interaction with law enforcement and has only one minor run-in with the law in its jurisdiction. News outlets named the man as Jared Lee Loughner.

Police were serving multiple search warrants in relation to the shooting and the individual they have in custody. A rumour suggested there might be someone else with a weapon at the scene but four hours later Rich Castigar said they dont have any information that suggests there was another shooter.

He said the weapon used was a pistol with an extended magazine, and that it was a "dynamic event that is still evolving."

NBC News reported Federal Judge John M. Roll was killed in the attack and there are reports a congressional staffer may have been killed, but details on the dead and injured are still sketchy.